An X-ray optical device with a variable aperture is discussed in US Patent Application Publication No. US 2004/0170250 A1. In this device, the variable aperture consists of a fixed portion and a movable portion that moves relatively to the fixed portion to change the size of an opening formed between the portions. These portions together are capable of shaping an X-ray beam passed through the aperture to a rectangular cross-section. As the movable portion is moved, the cross-section and position of the X-ray beam output from the device are changed. Notably, it is not possible to change the beam position while maintaining a consistent cross-section, or to change the beam cross-section while maintaining the position, unless both portions of the aperture are exchanged for aperture portions of different configurations.
A known X-ray diffractometer (the “X8 Proteum” produced by Bruker AXS, Madison, Wis.) uses a beam aperture that is mounted in a holder so that it is positioned perpendicularly to an incident X-ray beam. The aperture limits the cross-section of the beam, and its position can be adjusted in two orthogonal directions prior to its being fixed in place. This allows a user to fine-tune the position of the transmitted beam as part of an initial setup. Different beam cross-sections may also be selected by choosing from apertures with different shapes. However, to accomplish any of these changes requires time-consuming adjustments of the aperture, either by repositioning in two independent directions or by the manual exchange of the aperture.